The invention concerns a device for infrared (IR) spectroscopic investigation of internal surfaces of a body, for example of blood vessels with an IR spectrometer and with an endoscope with light guide means to illuminate the surfaces.
Such a device is known from WO 95/11624.
In endoscopes of such devices, scattered light is guided from internal surfaces of a body, mostly from blood vessels or internal body cavities via light guides to an external outside detector. Generally, glass fiber bundles are used as light guides. The light intensity of the detected scattered light and therefore the signal strength is thereby essentially proportional to the product of glass fiber cross sections which guide the light along the endoscope to the exposure, and the cross section of those glass fibers which collect the scattered light and guide it to the outside detector.
These prior art devices have therefore the disadvantage that for a given total cross section of the glass fibers only a fraction of the cross section can be used for illumination of the internal surfaces since the remaining glass fibers serve for guiding the collected light to the outside.
Apart from this, the collecting surface, i.e. the possible range of observation, is limited by the cross section of the collecting glass fibers and therefore relatively small in comparison to the total coating surface of the endoscope. The collecting fibers, suitable for spectroscopy (e.g. quartz) transfer the collected light only within a relatively narrow acceptance angle (generally a cone with .+-.10.degree.), leading to an additional strong spatial limitation of the light acceptance of scattered light by the endoscope.
From DE 27 46 614 A1, an endoscope is known with light guide means to illuminate investigated surfaces. The illuminating light for the endoscope comes from a cold light source or from illuminating diodes located at the distal end, but from a spectrometer. DE 27 46 614 A1 is only concerned with imaging, not with spectroscopy.
In U.S. Pat. No. 4,403,273, a rod-shaped reflection unit for the illumination system of an endoscope is presented which allows a particularly large field of view of more than 100.degree..
In DE-GM 19 20 775, at the distal end of an endoscope a fiber light guide is bent by about 90.degree., polished at its flat end and covered by an opal glass plate. Insertable optics enable sidewise directed observation.
In U.S. Pat. No. 5,058,568, it is suggested to use the protective metal cover weave or other elements of a flexible endoscope for electric connections, which can lead e.g. to a video chip at the distal end.
U.S. Pat. No. 4,674,515 describes a rotatable ultrasound head of an endoscope.
U.S. Pat. No. 4,782,818, finally, discloses an endoscope to illuminate internal body surfaces with visible light for therapeutic reasons.
It is therefore the purpose of the present invention to present an device of the kind described above which comprises, for otherwise equal conditions, an increased signal strength and thereby the possibility to reduce the measuring time for equal signal quality.